On Twitter, a user can follow another user, but the other user does not have to follow back. Twitter represents a non-directional network.

Hoping to lure more shoppers​ downtown, a city builds a new public parking garage in the central business district. The city plans to pay for the structure through parking fees. For a random sample of n = 42 weekdays, daily fees collected averaged $155, with a standard deviation of $12.  Complete parts a-c below.  Show as much work as possible.  When using your calculator, please specify the choice and your input values. a.  Create a 95​% confidence interval for the mean daily income this parking garage will generate.  Round your answers to two decimal place. (4pts.) b.  Interpret this confidence interval in the context of this problem (2 pts.) c.  The consultant who advised the city on this project predicted that parking revenues would average ​$160 per day. Based on your confidence​ interval, what do you think of the​ consultant’s prediction?​ Why? (4 pts.)

Suppose that the IQs of students at local university can be described by a normal model with mean 130 and standard deviation of 12 points. a)  Select 9 students at random from this university.  Describe the sampling distribution model for the sample mean

The time a gym’s members spend at the gym per week is believed to be normally distributed with a mean of 138 minutes and a standard deviation of 22 minutes.  You like to find the probability that a person spends more than 180 minutes at the gym per week. a.  Find the  z-score for  .  Round to two decimal place. (4 pts.) b. Graph the model and shade the region under the normal curve that illustrates the probability that a person spends more than 180 min per week at the gym. (4 pts.) c. What is the probability that a person spends more than 180 minutes at the gym per week?  justify your answer. (4 pts.)

You survey a sample of 1000 employees at a large company and record the age of each. The results are given in the frequency distribution table below.  If you select one employee at random, what is the probability the selected employee is more than 24 years old?        Age    Frequency       15-24           54       25-34          366       35-44          233       45-54          180       55-64          125  65 and over           42 If you select an employee at random, what is the probability the selected person is more than 24 years old?

Shifting data, by adding a constant to each data value, does not change the :

Based on a sample of 39 randomly selected years, a 90% confidence interval for the mean annual precipitation in one city is (45.36″ , 51.54″).  What is the margin of error for this interval?    

Mary, a statistics major, grows tomatoes in her spare time.  She keeps a record of the weight of each tomato she grows.  One tomato is 2 standard deviation heavier than the mean weight of her tomatoes.  Assume a Normal model is appropriate.  Approximately, what percentile is the weight of this tomato in?

Given independent random variables X and Y with means and standard deviations as shown, find the mean and standard deviation of  X-Y.  Justify your answer.      Mean        SD       X         86         4       Y         75          3

A recent newspaper article reported on Americans’ eating habits.  The article reported that only about one-third of American adults ate 2 or more servings of fruit per day, and only 26% ate 3 or more servings of vegetables per day.  Californians ate the most fruit, while Tennesseans ate the most vegetables.  The population in this study was: